One of my worm houses is in a concrete mixing tub. It was never used for concrete, but it is made from ABS plastic,which is tough and does not leech chemicals into water like many other plastics do.
It is important to bury your veggie scraps below the surface of the coconut coir. This prevents the scraps from attracting nasty bugs or fliers.
Bananas are exceptionally good at providing a population boost, but you will want a mix of foods for your little workhorses.
Many worms are very sensitive to typical outdoor chemicals like bug spray, pesticides, and other chemicals used on or near soil. Our homestead is chemical free and I literally cannot put a shovel in the ground without pulling up a handful of worms. Anywhere in my yard!
If you use chemicals in your yard or not, keeping worms can reduce your weekly garbage and redirect some of the smellier parts of your garbage can to a stink free worm farm. The,worm bedding becomes loaded with fertilizer Gold in the form of worm poop (what soil is made of).
Worms do not eat critter poop, citrus, dairy, or meat. While they do eat alliums like onion and garlic, they do not like those and those tend to stink through the bedding. They do like bread, but salt is an enemy of worms, so avoid crackers, pretzels, or chemical filled breads, if possible.
What do worms smell like? If done correctly with a few simple rules, they smell like fertile earth and freshly dug soil. If you do mess up with worms, they are fairly resilient and most problems are fixable by properly covering scraps or keeping the bedding moist, but not soaked.